Anesthesia Flashcards
Inhibitory neurotransmitter is the central nervous system?
GABA (γ-amino-butyric-acid)
First true BZD antagonist, synthesized in 1979?
Flumazenil
Mechanism of BZDs?
GABA exerts its inhibitory effect by opening the chloride ion channel on neuronal membranes, thus hyperpolarizing the cell membrane and making it less likely to depolarize. BZDs bind to benzodiazepine receptors presynaptically and postsynaptically, which facilitates the binding of GABA and potentiates its activity, causing CNS inhibition.
Effects of BZDs?
Anxiolysis, sedation-hypnosis, muscle relaxation (airway reflexes and tone), anterograde amnesia, and anticonvulsant activity
What is Verrill sign?
Relaxation causing ptosis of the eyelids to the point that the lower border of the upper eyelid bisected the pupil
What is the incidence of anterograde amnesia in patients who received 5 mg of midazolam?
Complete amnesia in 67% of patients.
Where are BZDs metabolized?
Liver metabolism, renal excretion.
Only true contraindications of BZDs?
Allergy and acute narrow-angle glaucoma.
Diazepam negative effects?
Many active metabolites, long elimination half-life (20-40 hrs), not water soluble (needs solvent for IV use- propylene glycol: risk phlebitis and venous thrombosis)
Midazolam advantages?
shorter half life (1-5 hrs), no active metabolites, water soluble.
Half life of flumazenil?
Roughly 1 hr, making resedation a risk.
Mechanism of flumazenil?
Competitive antagonist, interacts with the GABA-BZD complex and competitively displaces the BZD.
Name some natural opioids (2)
Morphine, codeine
Name semisynthetic opioids (4)
Hydrocodone, hydrocodone, oxycodone, heroin
Name synthetic opioids (4)
Fentanyl, tramadol, remifentanil, meperidine
Types of opioid receptors (3)
mu, delta, kappa
Primary desirable effect of opioids
analgesia
Undesirable effects of opioids
Histamine release, respiratory depression, hypotension, reduced gut transit or ileus, urinary retention, opioid withdrawal
Mechanism of respiratory depressant effect of opioids
Depression of brainstem response to increased CO2 and decreased O2. Low rate and large tidal volume.
Time to clear opioids from breast milk
Up to 96 hrs
Difference of meperidine effects from other opioids
atropine-like effects: tachycardia, decreased myocardial contractility, mydriasis
Meperidine duration of action
3-5 hours
Opioid most likely to cause histamine release
Meperidine, symptoms similar to anaphylaxis; also can cause vasodilation and hypotension
How much more potent than morphine is fentanyl
60-80 times more potent, also 2-3 times greater affinity at opioid receptor.
Fentanyl onset and clearance times
Rapid onset, rapid elimination (99% cleared from plasma in 60 min)
Which opioid receptor does remifentanil act on
mu selective
Pharmacokinetics of remifentanil (metabolization)
metabolized by tissue and plasma esterases which leads to extremely short half life.
Short acting opioid antagonist
Naloxone
Drug class of propofol
sedative hypnotic
Propofol is not water soluble and is formulated in a lipid emulsion containing:
soybean oil, egg phosphatide (lecithin), glycerol, preservative (EDTA)
Mechanism of action of propofol
Interacts with GABA receptors
Hiccups and myoclonic movements occur with which drug
methohexital, up to 90% of the time in patients who receive it
Cardiac effects of methohexital
tachycardia and hypertension, cardiac compensation for peripheral vasodilation
Potential epileptogenic
Methohexital
Clinical side effects of barbiturates
Respiratory depression, sedation/hypnosis, increased EEG activity, myocardial depression, decreased vascular resistance, excitatory motor effects.
